1. Field of the Invention
The present invention relates to a technique for an ultrasonic inspection, and more particularly to a technique for an ultrasonic inspection adopted when a penetration of a reactor pressure vessel is a portion to be inspected.
2. Description of the Related Art
As a technique for a nondestructive inspection of a solid material such as metal, inspection techniques using an ultrasonic wave (ultrasonic inspection or ultrasonic flaw detection) have been conventionally used. Known conventional techniques for an ultrasonic inspection of a reactor pressure vessel are described below.
For example, JP-A-07-244033 discloses a technique for an inspection of a welded stub. In the technique, an ultrasonic probe is placed on the inner surface of a penetration (a welded stub of a control rod drive mechanism attached to the bottom head of a reactor pressure vessel) of the reactor pressure vessel, and water is poured into the penetration, so that the inspection is performed with a water soak method.
In addition, JP-A-2005-300224 discloses a technique for an ultrasonic inspection of a penetration (a welded stub of a control rod drive mechanism) of the bottom head of a reactor pressure vessel by using an ultrasonic probe arranged inside the reactor or the reactor pressure vessel.
As described above, for a welded portion of a reactor pressure vessel, it has been common to use a conventional method of an ultrasonic inspection of a penetration of a reactor pressure vessel, the conventional method using an ultrasonic wave which is transmitted through a couplant such as water.